Subjects will include 20 clinically stable patients with Chronic Thromboembolic Pulmonary Hypertension (CTEPH) recruited from the Pulmonary Hypertension outpatient clinics at Hotel Dieu Hospital, Kingston, Ontario.
Pulmonary embolism, or clots blocking the blood vessels of the lungs, is a common clinical condition requiring treatment with blood thinners. In most patients, recovery is complete. A small proportion of patients, however, develop complications (high blood pressure in the lung circulation, i.e. pulmonary hypertension). Persisting breathlessness during activity is a common symptom in many of these patients and leads to a reduced ability to engage in daily physical activity. The reason for this activity-related breathlessness remains uncertain and is the main question of the proposed study. Using new sophisticated technology, the investigators will determine the root causes of perceived breathing difficulty. The investigators will test the idea that breathlessness is fundamentally the result of increased drive to breathe from control centers in the brain. The investigators will measure drive to breathe by measuring the electrical activity descending from the brain to the main muscle of breathing - the diaphragm. The investigators will discover if the increased drive to breathe is due to accumulation of carbon dioxide in the blood as a result of poor blood perfusion of areas of the lung due to the effects of blockage by clots. The investigators also will investigate whether weakness and fatigue of the muscles of breathing, as a result of the high breathing demands that are present in patients with blood clots in the lungs, contribute to breathlessness. With this information it is hopeful that better treatment options will be developed to relieve this distressing symptom.